DLC coating system and process and apparatus for making coating system

ABSTRACT

A process and an arrangement by means of which it is possible to generate a layer system for the protection against wear, for the protection against corrosion and for improving the sliding properties or the like, which has an adhesive layer for the arrangement on a substrate, a transition layer for the arrangement on the adhesive layer and a cover layer of an adamantine carbon, the adhesive layer including at least one element from the Group which contains the elements of the 4 th , 5 th  and 6 th  Subgroup and silicon, the transition layer comprising carbon and at least one element from the above-mentioned Group, and the cover layer consisting essentially adamantine carbon, the layer system having a hardness of at last 15 GPa, preferably at least 20 GPa, and an adhesion of at least 3 HF.

[0001] The present invention relates to a layer system for theprotection against wear, for the protection against corrosion and forimproving the sliding properties and the like, having an adhesive layerfor the arrangement on a substrate, a transition layer for thearrangement on the adhesive layer and a cover layer of an adamantinecarbon as well as to a process and an arrangement for producing suchlayer systems.

[0002] Despite the prominent properties of adamantine carbon layers (DLClayers), such as high hardness and excellent sliding properties, andmany years of worldwide research activities, it has not been possible toproduce pure DLC layers which, also in the case of larger layerthicknesses (>1 μm), exhibit a layer adhesion which is sufficient for anindustrial use in typical protection applications against wear and havea sufficient conductivity in order to be able to eliminate thehigh-frequency (HF) processes for their production which have manydisadvantages with respect to production techniques.

[0003] Typical protection applications against wear include, on the onehand, applications in the machine construction field, such as protectionagainst sliding abrasion, pitting, cold fusing, etc., particularly oncomponents with surfaces which move against one another, such as gears,pump and cup plungers, piston rings, injector needles, complete bearingsets or their individual components and many others, as well as, on theother hand, applications in the field of material processing for theprotection of the tools used for the cutting or forming machining aswell as in the case of injection molds.

[0004] In addition to the versatile application possibilities in thefield of protection against wear, the protection against corrosion isexplicitly mentioned here as another promising field of application ofsuch DLC layers.

[0005] Currently, because of the high internal tension and the resultingproblematic adhesion, particularly in the case of highly stressedsurfaces, in the protection against wear, pure DLC layers can bedeposited only with small layer thicknesses which are insufficient formany applications or must be changed in their properties by theadditional inclusion of foreign atoms, such as silicon, various metalsand fluorine. However, the resulting reduction of inherent layer tensionand the improvement of the adhesion has always been connected with aclear loss of hardness which, particularly in the field of theprotection against wear, can often have a negative effect on the servicelife of the respectively coated object.

[0006] In the case of plasma-supported processes customary today forproducing DLC layers, because of the high electric resistance of hardDLC layers, processes with an HF bias or HF plasma (in the followingHF=high frequency will apply to all frequencies >10 MHz), particularlywith the industrial frequency 13.56 MHz, are frequently used in order toavoid disturbing charges during the coating. The known disadvantages ofthis technique are interferences with electronically sensitive processcontrol units (HF feedback, transmitter effect, . . . ) which aredifficult to control; increased expenditures for avoiding HF flashovers;antenna effect of the substrates to be coated; and a resultingrelatively large minimal distance between the material to be coatedwhich prevents an optimal utilization of space and surface in thecoating chamber. Thus, in the case of HF processes, closest attentionhas to be paid to that fact that, for example, as a result of anexcessive loading density, incorrect substrate/holder spacing, etc.,there will be no overlapping of dark spaces, which causes harmfulsecondary plasmas. On the one hand, such secondary plasmas cause energysinks and thus additionally stress the plasma generators; on the otherhand, such local plasma concentrations frequently cause a thermaloverheating of the substrates and an undesirable graphitization of thelayer.

[0007] On the basis of the exponential dependence of the substratevoltage on the substrate surface calculated during HF processes,

U _(S) /U _(E) =C _(E) /C _(S)=(A _(E) /A _(S))⁴

[0008] wherein U is the voltage; C is the capacity; A is the surface;and S indicates the substrate and E indicates the counterelectrode, asthe substrate surface A_(S) rises, there is a considerable drop of thesubstrate voltage U_(S) accompanied by a significant rise of thedissipated energy. As a result, depending on the capacity of the usedgenerators, only a certain maximal surface can be coated. Otherwise,either sufficient power cannot be fed into the system or the potentialdifference (substrate voltage) cannot be adjusted to be sufficientlyhigh in order to achieve the ion plating effect required for welladhering dense layers.

[0009] In addition, on the system side in the case of HF-processes,additional equipment-related expenditures are usually required in orderto mutually dynamically adapt generator impedances and plasma impedancesby means of electric networks, such as a so-called matchbox, during theprocess.

[0010] In the following various processes and layer systems known fromthe state of the art will briefly be mentioned.

[0011] European Patent Document EP 87 836 discloses a DLC layer systemwith a 0.1-49.1% fraction of metallic constituents which is deposited,for example, by means of cathodic sputtering.

[0012] German Patent Document DE 43 43 354 A1 describes a process forproducing a multilayer Ti-containing layer system with a hard-materiallayer consisting of titanium nitrides, titanium carbides and titaniumborides as well as a friction-reducing C-containing surface layer, theTi fraction and N fraction being progressively reduced in the directionof the surface.

[0013] The process described in U.S. Pat. No. 5,078,848 uses a pulsedplasma beam for producing DLC layers. However, on the basis of thetargeted particle radiation from a source with a small outletcross-section, such processes are only conditionally suitable for theuniform coating of larger surfaces.

[0014] Various CVD processes and SiDLC/DLC mixed layers produced bymeans of such processes are described in the following documents:

[0015] European Patent Document EP-A-651 069 describes afriction-reducing protection system against wear of 2-5000 alternatingDLC and SiDLC layers. A process for depositing a-DLC layers with an Siintermediate layer and an adjoining a-SiC:H transition zone forimproving the adhesion is described in European Patent Document EP-A-600533. European Patent Document EP-A-885 983 and EP-A-856 592 alsodescribe various methods for producing such layers. For example, inEuropean Patent Document EP-A-885 983, the plasma is generated by aDC-heated filament and the substrates are acted upon by negative directvoltage or MF between 30-1,000 kHz (in the following MF=medium frequencyis the frequency range between 1 and 10,000 kHz).

[0016] U.S. Pat. No. 4,728,529 describes a method for depositing DLCwhile applying an HF plasma, during which the layer formation takesplace in a pressure range of between 10⁻³ and 1 mbar consisting of anoxygen-free hydrocarbon plasma to which, as required, a noble gas orhydrogen is admixed.

[0017] The process described in German Patent Document DE-C-195 13 614uses a bipolar substrate voltage with a shorter positive pulse durationin a pressure range between 50-1,000 Pa. As a result, layers aredeposited in the range of from 10 nm to 10 μm and of a hardness ofbetween 15-40 GPa.

[0018] A CVD process with a substrate voltage which is generatedindependently of the coating plasma is described in German PatentDocument DE-A-198 26 259, in which case, preferably bipolar but alsoother periodic changed substrate voltages are applied. However, thisrequires a relatively high-expenditure electric supply unit, because ithas to be provided in a twofold construction, for implementing theprocess.

[0019] Correspondingly, it is an object of the present invention toprovide relatively thick DLC layer systems with a high hardness and anexcellent adhesion which, in addition, still have a sufficiently highconductivity in order to be able to be deposited without HF bias, sothat a process and an arrangement can be used which do not require highexpenditures and are effective for industrial use. Correspondingly, itis also an object of the invention to provide a corresponding processand a corresponding arrangement.

[0020] This object is achieved by means of the layer having thecharacteristics of Claim 1 as well as the process according to Claim 11and the arrangement according to Claim 30. Advantageous furtherdevelopments are the object of the subclaims.

[0021] A DLC layer system is obtained by producing a layer with thefollowing layer construction.

[0022] An adhesive layer is situated directly on the substrate and hasan element from the group of elements of the IV, V and VI Subgroup aswell as Si. Preferably an adhesive layer of the elements Cr or Ti isused which were found to be particularly suitable for this purpose.

[0023] This layer is followed by a transition layer which is preferablyconstructed as a gradient layer in whose course the metal contentdecreases and the C content increases perpendicularly to the substratesurface.

[0024] The transition layer comprises essentially carbon and at leastone element from the group of elements forming the adhesive layer. Inaddition, hydrogen may be contained in a preferred embodiment.Furthermore, the transition layer as well as the adhesive layer containunavoidable impurities, as caused, for example, by atoms from thesurrounding atmosphere built into the layer, for example, the noblegases used in the production, such a argon and xenon.

[0025] When the transition layer is constructed in the form of agradient layer, the growth of the carbon in the direction of the coverlayer can take place by the increase of possibly different carbidicphases, by the increase of the free carbon or by a mixture of suchphases with the metallic phase of the transition layer. In this case, asknown to a person skilled in the art, the thickness of the gradient ortransition layer can be adjusted by adjusting the individual processramps. The increase of the C content and the decrease of the metallicphase can take place continuously or in steps; in addition, at least ina portion of the transition layer, a sequence of metal-rich and C-richindividual layers can be provided for the further reduction of layertensions. As a result of the above-mentioned constructions of thegradient layer, the material characteristics (such as the E module, thestructure, etc.) of the adhesive layer and of the final DLC layer areessentially continuously adapted to one another and the danger of acrack formation along an otherwise occurring metal or Si/DLC boundarylayer is therefore counteracted.

[0026] The end of the layer stack is formed by a layer which essentiallyconsists only of carbon and preferably hydrogen and which, in comparisonto the adhesion and transition layer, has a larger layer thickness. Inaddition to the carbon and hydrogen, noble gases, such as argon orxenon, can also occur here. However, it is important here thatadditional metallic elements or silicon are completely avoided.

[0027] The hardness of the entire DLC layer system is set at a valuegreater than 15 GPa, preferably greater than/equal to 20 GPa, and anadhesion of better than or equal to HF 3, preferably better than orequal to HF 2, particularly equal to HF 1, according to DVI 3824, Sheet4, is achieved. The hardness is determined by way of the Knoop HardnessMeasurement with 0.1 N load, that is HK_(0.1), so that 20 Gpa correspondto 2,000 HK_(0.1). The surface resistance of the DLC layer is betweenδ=10⁻⁶ Ω and δ=5 MΩ, preferably between 1 Ω and 500 kΩ, at an electrodespacing of 20 mm. Simultaneously, the present DLC layer distinguishesitself by the low coefficients of friction typical of DLC, preferablyμ≦in the pin/disk test. The layer thicknesses are all >1 μm,preferably >2 μm, the adhesive layer and the transition layer preferablyhaving layer thicknesses of from 0.05 μm to 1.5 μm, particularly of from0.1 μm to 0.8 μm, while the cover layer preferably has a thickness offrom 0.5 μm to 20 μm, particularly of from 1 μm to 10 μm.

[0028] The H content in the cover layer is preferably 5 to 30 atomicpercent, particularly 10 to 20 atomic percent.

[0029] In scanning electron microscope photos, DLC layer systemsdeposited according to the invention exhibit surfaces of fracture which,in contrast to the conventional DLC layers, have no glassy amorphousstructure but a fined-grained structure, the grain size preferably being≦300 nm, particularly ≦100 nm.

[0030] In tribological tests under a high load, the coating has amultiply increased service life in comparison to other DLC layers, suchas metal carbon layers, particularly WC/C layers. Thus, on an injectionnozzle for internal-combustion engines provided with a DLC layer, only aslight wear could be determined in a test after 1,000 h, whereas, in thesame test, a nozzle coated with WC/C failed after 10 h because of highsurface wear extending into the base material.

[0031] The layer roughness of the DLC layer according to the inventionpreferably has a value of Ra=0.01-0.04; Rz measured according to DINbeing <0.8, preferably <0.5.

[0032] The advantages of a DLC layer system according to the inventionwhich has the above-mentioned characteristics are the combinationachieved for the first time of large layer thicknesses with an excellentadhesion, which still have a sufficient conductivity for permitting arelatively simple process implementation in industrial production.

[0033] Despite the high hardness of >15 GPa, preferably ≧20 GPa, becauseof its structure and the process steps according to the invention, thelayer exhibits a clearly improved adhesion. Here, conventional layersystems require a doping in the function layer (DLC) in order to reducethe layer tension, which, however, also reduces the hardness.

[0034] Also scanning electron microscope fracture photos of the layeraccording to the invention exhibit a fine-grained straight fracturesurface in contrast to the previously known DLC layers which have thetypical fracture shape of an amorphous brittle layer with partiallyconchoidal eruptions. Layers having the above-described property profileare particularly suitable for applications in machine construction, as,for example, for coating highly stressed pump and cup plungers and valvegears, cams and camshafts, as used for motor vehicle combustion enginesand transmissions, but also for the protection of highly stressed gears,plungers, pump spindles and other components, in the case of which aparticularly hard and smooth surface is required which has good slidingproperties.

[0035] In the tool field, because of their great hardness and verysmooth surface, these layers can advantageously be used mainly forforming (pressing, punching, deep-drawing, . . . ) and injection moldingtools but also, with certain limitations when machining iron materials,for cutting tools, particularly if a particularly low coefficient offriction paired with a great hardness is required for the application.

[0036] The process according to the invention for producing DLC layersystems is characterized by the following features.

[0037] The parts to be coated are cleaned in a manner known for PVDprocesses and are mounted on a holding device. In contrast to HFprocesses, holding devices can advantageously be used here with—adaptedaccording to the respective particle geometry—1, 2 or 3 essentiallyparallel axes of rotation, whereby a greater loading density can beachieved. The holding device with the parts to be coated is moved intothe process chamber of a coating system and, after the pumping down to astarting pressure of less than 10⁻⁴ mbar, preferably 10⁻⁵ mbar, theprocess sequence is started.

[0038] The first part of the process—cleaning the substrate surfaces—iscarried out, for example, as a heating process in order to remove thevolatile substances still adhering to the surface of the parts. For thispurpose, similar to German Patent Document DE 28 23 876, a noble gasplasma is preferably ignited by means of a high-current/low-voltagedischarge between one or several filaments arranged in an ionizationchamber adjoining the process chamber and applied to a negativepotential and the holding devices with the parts which is applied to apositive potential. This causes an intensive electron bombardment andtherefore a heating of the parts. In this case, as in German PatentDocument DE 44 37 269, it was found to be particularly advantageous touse an AR/H2 mixture because a cleaning effect of the parts surfaces isachieved by the reducing effect of the hydrogen. In this case, thehigh-current/low-voltage arc discharge can be guided by a static oradvantageously essentially locally variably moved magnetic field.Instead of the above-described ionization chamber, a hollow cathode oranother known ion or electron source can also be used.

[0039] As an alternative, other heating processes, such as radiantheating or inductive heating, can naturally also be used.

[0040] After a temperature level has been reached which is to bedetermined according to the base material, in addition or as analternative, an etching process can be started as a cleaning process inthat a low-voltage arc is ignited, for example, between the ionizationchamber and an auxiliary anode, and the ions are drawn onto the parts bymeans of a negative bias voltage of from 50 to 300 V. There, the ionsbombard the surface and remove residual impurities. A clean surface istherefore obtained. In addition to noble gases, such as argon, theprocess atmosphere can also contain hydrogen.

[0041] Furthermore, the etching process can also take place by theapplication of a pulsed substrate bias voltage without or with theassistance of an above-described low-voltage arc, preferably a mediumfrequency bias in the range of from 1 to 10,000 kHz, particularlybetween 20 and 250 kHz, being used.

[0042] In order to ensure the adhesion of the DLC layer system on thesubstrate, a preferably metallic adhesive layer particularly consistingof Cr or Ti is vapor-deposited by means of a known PVD or plasma CVDprocess, such as, for example, arc-type vaporizing, various ion platingprocesses, however, preferably by cathodic sputtering, of at least onetarget. For aiding the vapor depositing, a negative substrate biasvoltage is applied to the substrate. The ion bombardment and theresulting layer densification during the sputtering process canadditionally be aided by a parallel-operated low-voltage arc and/or amagnetic field applied for stabilizing and intensifying the plasma,and/or by applying a DC bias voltage to the substrate or by applying amedium frequency bias between the substrate and the process chamber inthe range of from 1 to 10,000, particularly between 20 and 250 kHz.

[0043] In a known manner, the thickness of the adhesive layer is set bya selection of the sputtering or vapor depositing time and powercorresponding to the respective system geometry.

[0044] For example, in the case of the present system geometry describedbelow, Cr is sputtered for the duration of 6 minutes from twoadvantageously opposite targets at a pressure of between 10⁻⁴ and 10⁻³mbar, a substrate bias of U_(bias)=−75 V and a power of approximately 8kW in an Ar atmosphere.

[0045] According to the invention, after the application of the adhesivelayer, by applying a transition layer, a transition, which is as fluidas possible is ensured between the adhesive layer and the DLC layer.

[0046] The application of the transition layer takes place such that, inaddition to the plasma-aided vapor-depositing of the adhesive layerconstituents, isochronously, carbon is precipitated from the gas phase.This preferably takes place by way of a plasma CVD process in which acarbon-containing gas, preferably a carburetted hydrogen gas,particularly acetylene, is used as the reaction gas.

[0047] During the application of the transition layer, an, inparticular, “pulsed” medium-frequency substrate bias voltage is appliedto the substrate and a magnetic field is superimposed.

[0048] For the preferred formation of a gradient layer, during theapplication of the transition layer, the fraction of the carbonprecipitation is increased in steps or continuously as the thickness ofthe transition layer increases, until finally essentially only a carbonprecipitation still takes place.

[0049] In this process stage, the adamantine carbon layer is thengenerated as the cover layer by a plasma CVD precipitation of carbonfrom the gas phase, in which case a carbon-containing gas, preferably acarburetted water gas, particularly acetylene, is used as the reactiongas. Simultaneously, a substrate bias voltage continues to be maintainedon the substrate, and the superimposed magnetic field is maintained.

[0050] In a preferred embodiment, the reaction gas for depositing carbonfor forming the transition layer and the cover layer made of adamantinecarbon may, in addition to the carbon-containing gas, contain hydrogenand noble gas, preferably argon or xenon. The set pressure in theprocess chamber in this case is between 10⁻⁴ mbar to 10⁻² mbar.

[0051] During the depositing of the cover layer made of adamantinecarbon, the fraction of the carbon-containing gas is preferablyincreased and the fraction of the noble gas, particularly argon, ispreferably lowered.

[0052] The substrate bias voltage, which is applied during the processsteps for vapor depositing the adhesive layer, applying the transitionlayer and depositing the cover layer on the substrate may, particularlyduring the formation of the transition layer and of the cover layer, bean alternating voltage (AC), a direct voltage (DC) superimposed with ACor pulse, or a modulated direct voltage, as particularly a unipolar(negative) or bipolar substrate bias voltage, which is pulsed in amedium frequency range of from 1 to 10,000 kHz, preferably from 20 to250 kHz. In this case, the pulse form may be sinusoidal or asymmetrical,so that long negative and short positive pulse periods or large negativeand small positive amplitudes are applied.

[0053] Furthermore, preferably during the entire coating process, alongitudinal magnetic field with a uniform course of magnetic flux isset, the magnetic field being variable laterally and/or spatially,continuously or in steps.

[0054] Preferably, if a DC bias was used for applying the adhesivelayer, when the transition layer is applied, a medium frequencygenerator is first connected to the holding device, which mediumfrequency generator emits its voltage pulses (a regulating bycontrolling the fed power is also possible, but not preferred) in theform of a sinusoidal or of another bipolar or unipolar signal course. Inthis case, the used frequency range is between 1 and approximately10,000 kHz, preferably between 20 and 250 kHz; the amplitude voltage isbetween 100 and 3,000 V, preferably between 500 and 2,500 V. The changeof the substrate voltage is preferably carried out by switching-over agenerator which is designed especially for the emission of direct andmedium frequency voltage. In another advantageous embodiment, a mediumfrequency voltage is applied to the substrates also for theimplementation of the etching and adhesive layer process. When a bipolarsubstrate voltage is used, it was found to be particularly advantageousto apply asymmetrical pulse forms; for example, the positive pulse canbe applied more briefly or with a lower voltage than the negative pulse,because the electrons follow the field more rapidly and, because oftheir low mass, when impacting, result mainly in an additional heatingof the parts, which may result in damage by overheating particularly inthe case of temperature-sensitive base materials. Also in the case ofdifferent signal courses, this danger can be counteracted by providing aso-called “OFF time”, in the case of which a zero signal is appliedbetween the application of individual or several signal periods with apower fraction (=“ON time”).

[0055] Isochronously or with a time delay after the application of themedium frequency signal, when a DC bias is used for the application ofthe adhesive layer, or after the vapor depositing of the layer thicknessdesired for the adhesive layer when a medium frequency bias is used, acarburetted hydrogen gas, preferably acetylene, is admitted into therecipient by means of a gas flow which rises in steps or preferablycontinuously. Also isochronously or with a possibly different timedelay, the power of the at least one metallic or Si target is broughtdown in steps or continuously. Preferably the target is brought down toa minimum power, which can be easily determined by a person skilled inthe art according to the achieved hydrocarbon flow, at which minimumpower a stable operation is still possible without symptoms of poisoningby the reactive gas. Subsequently, the at least one target is shieldedagainst the process chamber preferably means of one or several movablyarranged screens, and is switched off. This measure largely prevents anoccupation of the target with a DLC layer, whereby a sputtering freebetween individual DLC coating batches, which is otherwise necessary,can be eliminated. In the case of the next batch to be implemented, itis sufficient to provide a bringing-up of the at least one target whilethe screens are closed in order to again achieve a completely baretarget surface suitable for the application of the adhesive layer.

[0056] A significant contribution to the stabilizing of the DLC coatingprocess according to the invention is made by forming a longitudinalmagnetic field. This will take place—unless it was already used in thepreceding process step for applying the adhesive layer—essentiallyisochronously with the switching-over of the substrate voltage to themedium frequency generator. The magnetic field is constructed such thata magnetic flux course exists in the process chamber which is as uniformas possible. For this purpose, preferably by two electromagnetic coilsessentially bounding the process chamber on opposite sides, current isintroduced such that a mutually reinforcing magnetic field is createdwhich is directed in the same direction at both coils. In the case ofsmaller chamber dimensions, a sufficient effect may possibly also beachieved by means of only one coil. As a result, an approximatelyuniform distribution of the medium frequency plasma is achieved overlarger chamber volumes. Nevertheless, as a result of differentgeometries of the parts to be coated and of the holding devices,occasional secondary plasmas may be formed if certain geometrical andelectromagnetic marginal conditions are met. This can be counteracted bya magnetic field which is variable with respect to time and space inthat the coil currents are displaced together with one another orpreferably against one another. For example, a current intensity I firstflows for 120 seconds through the first coil which is stronger than thatflowing through the second coil. During the subsequent 90 seconds, thecurrent intensity is inverse; that is, the second magnetic field isstronger than the first magnetic field. These magnetic field adjustmentscan take place periodically, as described, in steps or continuously andthus, by the suitable selection of the corresponding coil currents, theforming of stable secondary plasmas can be avoided.

[0057] In contrast to the prior art, it is possible only as a result ofthe use of the magnetic field and the resulting significant increase ofthe plasma intensity to achieve, also in low pressure ranges of, forexample, from 10⁻³ to 10⁻² mbar, a stable CVD process for depositingpure DLC layers with high depositing rates in the range of from 0.5 to5, preferably between 1-4 μm/h. In this case, in addition to thesubstrate current, the plasma intensity is also directly proportional tothe activation of the magnetic field. Additionally, both parametersdepend on the size of the offered surfaces acted upon by means of abias. By applying lower process pressures, smoother layers with a lowernumber of growth defects and a lower contamination by disturbingexternal elements can be deposited.

[0058] In addition to being a function of the process parameters, thegrowth rate also depends on the loading and the holding device. It isparticularly important in this case whether the parts to be coated,rotating once, twice or three times, are fastened on magnetic holdingdevices or are clamped or fitted in. The overall mass and the plasmatransmissibility of the holding devices is also significant. Thus, forexample, by means of light-weight holding devices, for example, by usingspoke plates instead of plates made of a solid material, higher growthrates and overall a better layer quality is achieved.

[0059] For the further increase of the plasma-reinforcing magneticfield, in addition to the longitudinal magnetic field (far field) whichpenetrates the whole process chamber, additional local magneticfields—so-called near fields—can be provided. An arrangement isparticularly advantageous in the case of which, in addition to at leastone magnetron magnetic system of the at least one target, additional,preferably permanent magnetic systems are mounted on the walls boundingthe plasma chamber, which have a similar or the same magnetic effect asthe at least one magnetron magnetic system. In this case, either allmagnetron and additional magnetic systems can have the same constructionor preferably a reversal of the polarities can take place. As a result,it is possible to construct the individual near fields of the magneticand magnetron magnetic systems just like a magnetic enclosuresurrounding the process chamber and thus prevent an absorption of thefree electrons on the walls of the process chamber.

[0060] It is only possible to produce a layer as described above by acombination of the important characteristics of the inventive process.Only the use of plasmas stabilized by magnetic fields as well as thecoordinated use of the substrate bias voltage permit the use of theholding devices optimized for conventional PVD processes with a highpacking density and process reliability. The process shows how thecourse and the combination of direct current and medium frequencyplasmas can optimally be used for depositing a DLC layer.

[0061] Furthermore, the above-mentioned object is achieved by providingan arrangement for the implementation of the coating process accordingto one of Claims 10 to 26, the arrangement comprising a vacuum chamberwith a pumping system for generating a vacuum in the vacuum chamber,substrate holding devices for receiving the substrates to be coated, atleast one gas supply unit for the metered addition of process gas, atleast one vaporizer system for providing coating material for vapordepositing, an arc generating device for igniting a direct voltagelow-voltage arc, a system for generating a substrate bias voltage, andat least one or several magnetic field generating devices for forming amagnetic far field.

[0062] The magnetic field generating devices are preferably formed by atleast one Helmholtz coil, preferably a pair of Helmholtz coils.

[0063] When Helmholtz coils are used, the magnetic field which can begenerated and the magnetic flux density can be controlled locally aswell as with respect to time by the current intensity in the coils.

[0064] Furthermore, the arrangement comprises a device for generating asubstrate bias voltage which continuously or in steps can change theapplied substrate bias voltage and correspondingly can also be operatedin a bipolar or unipolar manner. In particular, the device is suitablefor generating a substrate bias voltage which is pulsed in the mediumfrequency range.

[0065] The vaporizing devices used in the arrangement comprise sputtertargets, particularly magnetron sputter targets, arc sources, thermalevaporators and the like. It is advantageous that the vaporizer devicecan be separated from the remaining process chamber, for example, bymeans of swivellable screens.

[0066] The arrangement advantageously has a substrate heater in the formof an inductive heater, a radiant heating system or the like, in orderto be able to clean the substrates in a heating step before the coating.However, the igniting of a plasma is preferably used.

[0067] Among other things, a low-voltage arc generating device isprovided in the arrangement for this purpose, which comprises an ionsource with a filament, preferably a refractory filament made oftungsten, tantalum or the like, in an ionization chamber as well as ananode and a direct voltage supply. In this case, the ion source isconnected with the negative pole of the direct voltage supply.Preferably, the positive pole of the direct voltage supply canoptionally be connected with the anode or the substrate holding devices,so that a low-voltage arc can be ignited between the ion source and theanode or the ion source and the substrates. Similar to the vaporizerdevice, the ion source can also be separated from the actual processchamber, for example, by means of a hole metal plate made of tungsten,tantalum or a similar refractory metal.

[0068] In order to permit a uniform coating process for all sides of thesubstrates, it is also provided that the substrate holding devices aremovable and can preferably rotate about at least one or several axes.

[0069] As a result of the advantageous combination of themedium-frequency substrate voltage supply and a Helmholtz coilarrangement, which can also be implemented by laterally mounted coilscomprising two opposite targets, it is, for the first time possible atan industrial scale to utilize also in the case of low pressures astable medium frequency plasma for carrying out a DLC process. Incontrast to DLC layers produced by means of other systems, the thusproduced layers have considerably improved properties.

[0070] By means of the present coating arrangement and theabove-described process, thick pure DLC layers with an excellentadhesion can be produced for the first time. In addition, when theprocess parameters are changed, a majority of the previously knownplasma processes for producing metal carbon or mixed layers with otherelements, such as silicon or F, and for producing multipart layers orsimple known layer systems deposited by means of PVD and/or CVDprocesses can be carried out.

[0071] Additional advantages, features and characteristics of theinvention are illustrated by means of the following detailed descriptionof preferred embodiments by means of the attached drawings.

[0072]FIG. 1 is a schematic cross-sectional view of the arrangementaccording to the invention;

[0073]FIG. 2 is a schematic top view of the arrangement of the inventionaccording to FIG. 1;

[0074]FIG. 3 is a schematic view of the influence of the coil current onthe substrate current;

[0075]FIG. 4 is a schematic view of the process parameter gradientlayer;

[0076]FIG. 5 is a schematic view of the process parameter DLC layer;

[0077]FIG. 6 is a scanning electron microscope fracture photo of a DLClayer according to the invention.

[0078]FIG. 1 is a schematic cross-sectional view of the process chamber1 of a coating arrangement according to the invention. The parts 2 to becoated are mounted on one or several holding devices 3 which comprisesdevices for generating an at least single rotation 4, as required, adouble rotation 5 of the parts. In a particularly advantageousembodiment, the holding devices 3 are positioned on a carrousel 17 whichadditionally can be rotated about the axis 6 of the arrangement.

[0079] By way of gas inlets 8, the different process gases, particularlyAr and acetylene, can be fed into the process chamber by means ofsuitable regulating devices which are not shown here.

[0080] A pumping stand 9 which is suitable for a high vacuum is flangedto the chamber.

[0081] An ion source 10 is preferably arranged in the area of the axisof the arrangement and is connected to the negative output of a directvoltage supply 11. Depending on the process step, the positive pole ofthe direct voltage supply 11 can be applied by way of a switch 12 to thecarrousel 7 and to the holding device 3 and the parts 2 electricallyconnected therewith (heat process) or to the auxiliary anode 13 (etchingprocess or, as required, also during the coating processes).

[0082] On the walls of the process chamber 1, at least one vaporizersource 14, preferably a magnetron or an arc vaporizer, is provided forapplying the adhesive and gradient layer. In another embodiment of thevaporizer source 14, which is not shown here, this vaporizer source 14can be mounted as an anodically switched pot centrally in the floor ofthe process chamber 1. In this case, the vaporization material ischanged into the gas phase for producing the transition or gradientlayer by means of heating by the low-voltage arc 15.

[0083] Furthermore, an additional electric voltage supply 16 is providedby means of which a periodically variable medium frequency voltage inthe range of between 1 to 10,000, preferably between 20 and 250 kHz, canbe applied to the substrates.

[0084] The electromagnetic coils 17 for generating a longitudinalmagnetic field penetrating the plasma space are arranged on oppositeboundary walls of the process chamber 1 and are fed in the samedirection by at least one, preferably two separate DC voltage sourceswhich are not shown here in detail.

[0085] As additional measures for intensifying and more uniformlyshaping the magnetic field and thus the MF plasma 18, magnetic systems20 for forming several magnetic near fields 21 can be mounted on theside walls 19 of the plasma chamber 1. In this case, advantageously andoptionally while including the at least one magnetron magnetic system22, as illustrated, for example, in FIG. 2, alternately magnetic systemswith an NSN and an SNS polarity are arranged and thus a magnetictunnel-shaped loop-shaped inclusion of the plasma is caused in theprocess chamber.

[0086] The magnetic systems 20 for the generating the near field arepreferably constructed as magnetron magnetic systems.

[0087] The individual systems of the coating arrangement areadvantageously entered into a relationship with one another by a processcontrol. As a result, it is possible, in addition to the basic functionsof a vacuum coating arrangement (pumping stand control, safety controlcircuits), to mutually adapt in a flexible manner the variousplasma-generating systems, such as magnetrons with the magnetron supplynot described here in detail, the ionization chamber 1 and the auxiliaryanode 13 or the carrousel 7 and the direct-voltage supply 11, as well asthe carrousel 7 and the medium frequency generator 16 as well as thecorresponding adjustment of the gas flows, as well as the controlling ofthe optionally different coil currents and to optimize them fordifferent processes.

[0088]FIG. 3 illustrates the relationship between the substrate currentand the coil current when using Helmholtz coils for building up amagnetic field. It was found that the substrate current and thus theplasma intensity are directly proportional to the coil current and thusto the magnetic field buildup. This is clearly demonstrated by thepositive effect of a superimposed magnetic field.

[0089] As an example, FIG. 4 illustrates the course of individualparameters during the application of a gradient layer: While otherwisethe parameters remain the same in comparison to the adhesive layer, thesubstrate bias is switched over from direct current to medium frequencywith a preferred amplitude voltage of between 500 and 2,500 V and afrequency between 20 and 250 kHz. After approximately 2 minutes, anacetylene ramp is started at 50 sccm and is raised over a time period ofapproximately 30 minutes to 350 sccm. Approximately 5 minutes afterswitching on the medium frequency generator, the power of the used Crtarget is reduced to 7 kW; after another 10 minutes, it is reduced to 5kW and is held constant there for another 2 minutes. Subsequently,screens are moved in front of the targets and these are switched off,whereby the depositing of the “pure” DLC layer starts which isconstructed essentially of carbon atoms, of low quantities of hydrogenand of still lower quantities of argon atoms.

[0090] For this purpose, in the simplest case, the process can becompleted with switched-off vaporizing sources, but otherwise with thesame parameters as in the case of the preceding gradient layer. However,it was found to be advantageous to increase in the course of thedeposition of the pure DLC layer either the hydrocarbon fraction in thegas flow, to lower the noble gas fraction or, particularly preferably,to carry out both measures jointly. Here also, a forming of alongitudinal magnetic field, as described above, again has a specialsignificance for maintaining a stable plasma.

[0091] In the manner of examples, FIGS. 4 and 5 show the course ofindividual parameters during the application of the pure DLC layer:After the switching-off of the used Cr target, while the mediumfrequency supply is adjusted to remain constant and the argon flowremains the same, the acetylene ramp started during the gradient layeris increased for approximately 10 minutes uniformly to a flow betweenapproximately 200 and 400 sccm. Subsequently, for a time period of 5minutes, the argon flow is continuously reduced to a flow betweenapproximately 0 and 100 sccm. During the next 55 minutes, the process iscompleted while the adjustments remain the same.

[0092]FIG. 6 is a scanning-electron-microscopic photo of a fracturesurface of a DLC layer system according to the invention. It is clearlydemonstrated that a fine-grained structure exists in the area of thecover layer made of an adamantine carbon, so that the DLC layer has apolycrystalline character.

EMBODIMENT OF THE INVENTION IN THE EXAMPLE Process Example 1

[0093] Heating Process

[0094] The process chamber is pumped down to a pressure of approximately10⁻⁵ mbar and the process sequence is started. As a first part of theprocess, a heating process is carried out in order to bring thesubstrates to be coated to a higher temperature and to remove volatilesubstances from the surface. In this process, an Ar hydrogen plasma isignited by means of a low-voltage arc between the ionization chamber andan auxiliary anode. The following Table 1 shows the process parametersof the heating process: Ar Flow  75 sccm Substrate Bias Voltage [V]  0Current of the Low-Voltage Arc 100 A Hydrogen Flow 170 sccm CurrentUpper Coil Pulsating between 20 and 10 A Current Lower Coil PulsatingDiametrically Opposed between 2 and 5 A Period between Max. and Min. 1.5min. Coil Current Heating Time  20 min.

[0095] The Helmholtz coils are used for activating the plasma and arecyclically controlled. In this case, the current of the upper coil isvaried with a period of 1.5 min. between 20 and 10 A; the current of thelower coil varies with the same timing in a diametrically oppositemanner between 5 and 20 A.

[0096] The substrates heat up in the process and the disturbing volatilesubstances adhering to the surface are driven into the gas atmosphere,where they are sucked off by the vacuum pumps.

[0097] Etching Process

[0098] When a uniform temperature has been reached, an etching processis started in that the ions are drawn from the low voltage arc by meansof a negative bias voltage of 150 V onto the substrates. The alignmentof the low-voltage arc and the intensity of the plasma are aided in thiscase by the pair of Helmholtz coils mounted in a horizontal alignment.The following table shows the parameters of the etching process Ar Flow75 sccm Substrate Voltage −150 V Low-Voltage   150 A Arc Current

[0099] Cr Adhesive Layer

[0100] The application of the Cr adhesive layer is started in that theCr magnetron sputter targets are activated. The Ar gas flow is adjustedto 115 sccm. The Cr sputter targets are triggered by means of a power of8 kW and the substrates are moved past the targets for a time of only 6minutes. The occurring pressure range will then be between 10⁻³ mbar and10⁻⁴ mbar. The sputtering process is aided by the connection of thelow-voltage arc and the application of a negative DC bias voltage of 75V to the substrate.

[0101] After half the Cr sputtering time, the low voltage arc isswitched off and the depositing is carried out for the remainder of theCr sputtering time only by means of the plasma active in front of the Crtarget.

[0102] Gradient Layer

[0103] After the expiration of this time, by means of switching on asine wave generator, a plasma is ignited, acetylene gas with an initialpressure of 50 sccm is admitted and the flow is increased each minute by10 sccm.

[0104] In this case, the sine plasma generator is set at a frequency of40 kHz to an amplitude voltage of 2,400 V. The generator ignites aplasma discharge between the substrate holding devices and the housingwall. In this case, the Helmholtz coils mounted on the recipient areboth activated by means of a constant current flow of 3 A in the lowercoil and 10 A in the upper coil. In the case of an acetylene flow of 230sccm, the Cr targets are deactivated.

[0105] DLC Coating

[0106] When the flow of the acetylene has reached the value of 350 sccm,the Ar flow is reduced to a value of 50 sccm.

[0107] The table shows the parameters of the example in an overview:Argon Flow   50 sccm Acetylene Flow   350 sccm Excitation Current UpperCoil   10 A Excitation Current Lower Coil    3 A Voltage Amplitude 2,400V Excitation Frequency f   40 kHz

[0108] Under these conditions, a high depositing rate is ensured and theionization of the plasma is maintained by means of the Ar gas. Thedepositing rate which now occurs in the coating process will be in therange of between 0.5 and 4 μm/h, which also depends on the surface to becoated in the process chamber.

[0109] After the expiration of the coating time, the sine wave generatorand the gas flow are switched off, and the substrates are removed formthe process chamber.

[0110] The properties of the forming layer are illustrated in thefollowing table:

Properties Example 1

[0111] Micro Hardness >2,200 HK Depositing Rate 1-2 μm/h Adhesion HF1Resistance <10 kOhm Hydrogen Content 12% Coefficient of Friction 0.2Internal Tension Approx. 2 GPa Fraction Behavior Not glassy

Process Example 2

[0112] Process Example 2 provides an implementation similar toExample 1. In contrast to Example 1, the plasma is generated by abipolar pulse generator. The excitation frequency is at 50 kHz with anamplitude voltage of 700V.

[0113] The table shows the parameters of the 2nd example. Argon Flow  50sccm Acetylene Flow 350 sccm Excitation Current Upper Coil  10 AExcitation Current Lower Coil  3 A Voltage Amplitude 700 V ExcitationFrequency f  50 kHz

[0114] The produced coating has a hardness of 25 GPa, an adhesion of HF1and results in a coefficient of friction of 0.2.

Properties Example 2

[0115] HK >2,400 Depositing Rate Approx. 1.5 μm/h Adhesion HF1Resistance <500 kOhm Hydrogen Content 13% Coefficient of Friction 0.2Internal Tension Approx. 3 GPa

Process Example 3

[0116] Process Example 3 provides an implementation similar toExample 1. In contrast to Example 1, the plasma is excited by a unipolarpulse voltage. The parameters of the test are shown in the followingtable. Argon Flow   50 sccm Acetylene Flow   350 sccm Excitation CurrentUpper Coil   10 A Excitation Current Lower Coil   10 A Voltage Amplitude1,150 V Excitation Frequency f   30 kHz

[0117] The produced coating has the properties described in thefollowing table.

Properties Example 3

[0118] Micro Hardness 2,500 HK Depositing Rate Approx. 1.8 μm/h AdhesionHF1 Resistance <1 kOhm Hydrogen Content 12 to 16% Coefficient ofFriction 0.2 Internal Tension Approx. 2 GPa

Process Example 4

[0119] In comparison to Process Example 1, a process without assistanceby a longitudinal magnetic field was carried out in Example 4. Thecurrent flowing through the two coils was reduced to a value of 0 A. Thetable shows the process parameters. Argon Flow   50 sccm Acetylene Flow  350 sccm Excitation Current Upper Coil    0 A Excitation Current LowerCoil    0 A Voltage Amplitude 2,400 V Excitation Frequency f   40 kHz

[0120] A plasma is obtained which, in comparison to Example 1, is stableonly at higher pressures than in Example 1; is inhomogeneouslydistributed over the process chamber, and is influenced by geometricaleffects. A depositing rate therefore occurs which is inhomogeneous inthe process chamber and lower than in Example 1 because of the setprocess pressure. At the endeavored process pressures, a plasmaformation was not possible without the use of a second plasma source,such as a target or the connection of the filament. The plasma in theprocess chamber could be stabilized only by the use of the Helmholtzcoils and a homogeneous deposition could be achieved over the height ofthe process chamber. Without the use of coils, a plasma ignited in therange of the ionization chamber, where locally high temperatures aregenerated and destruction has to be feared.

Properties Example 4

[0121] HK Inhomogeneous 1,300-2,500 Depositing Rate InhomogeneousResistance Inhomogeneous Adhesion Cannot be determined

List of Reference Numbers

[0122]1 Process chamber

[0123]2 parts to be coated

[0124]3 holding device

[0125]4 single rotation

[0126]5 double rotation

[0127]6 axis of arrangement

[0128]7 carrousel

[0129]8 gas inlet

[0130]9 pumping stand

[0131]10 ion source

[0132]11 direct-voltage supply

[0133]12 switch

[0134]13 auxiliary anode

[0135]14 vaporizer source

[0136]15 low-voltage arc

[0137]16 voltage supply

[0138]17 electromagnetic coil

[0139]18 MF plasma

[0140]19 side wall

[0141]20 magnetic systems

[0142]21 near fields

[0143]22 magnetron magnetic system

1-42. (Cancelled).
 43. Process for producing a layer system for theprotection against wear, for the protection against corrosion and forimproving the sliding properties and the like, having an adhesive layerfor the arrangement on a substrate, a transition layer for thearrangement on the adhesive layer and a cover layer of an adamantinecarbon, said process comprising a) charging the substrate into a vacuumchamber and pumping down to a vacuum of a pressure of less than 10⁻⁴mbar, preferably 10⁻⁵ mbar, b) cleaning a surface of the substrate, c)plasma-aided vapor-depositing of the adhesive layer on the substrate, d)applying the transition layer to the adhesion layer by the simultaneousplasma-aided vapor depositing of the adhesion layer constituents anddepositing carbon from the gas phase, e) applying the adamantine carbonlayer on the transition layer by a plasma-aided depositing of carbonfrom the gas phase, at least during process steps c), d) and e), asubstrate bias voltage being applied to the substrate, and at leastduring process steps d) and e), the plasma being stabilized by amagnetic field.
 44. Process according to claim 43, the cleaning of thesubstrate surface comprises at least one of a heating step and anetching step.
 45. Process according to claim 44, wherein the heatingstep takes place by at least one of radiant heating, inductive heatingand by electron bombardment.
 46. Process according to claim 45, whereinthe electron bombardment is caused by the ignition of a low-voltage arcand the simultaneous application of a continuous AC or AC superimposedbias voltage, as particularly a pulsed positive substrate bias voltage.47. Process according to claim 44, wherein the etching step is carriedout by ion etching, by means of at least one of a noble gas and hydrogenas the process gas, a low-voltage arc being ignited and a continuousnegative substrate bias voltage being applied to the substrate. 48.Process according to claim 44, wherein the etching step is carried outby ion etching by means of at least one of a noble gas and hydrogen as aprocess gas, and an AC or AC superimposed substrate bias voltage, beingapplied.
 49. Process according to claim 44, wherein the vapor depositingof the adhesive layer takes place one of by PVD processes, plasma CVDprocesses, cathodic sputtering and evaporation out of crucible by meansof a low voltage arc.
 50. Process according to claim 49, wherein thevapor depositing of the adhesive layer is aided by an additionallow-voltage arc discharge and a negative substrate bias voltage isapplied to the substrate.
 51. Process according to claim 49, the vapordepositing of the adhesive layer is aided by an additional pulsedsubstrate bias voltage, an AC or AC superimposed bias voltage,particularly a pulsed substrate bias voltage in a medium frequency rangeof from 1 to 10,000 kHz.
 52. Process according to claim 43, wherein, forthe ignition of a plasma, a noble gas or a noble gas/hydrogen mixture,is fed into the vacuum chamber.
 53. Process according to one of claim43, wherein the transition layer is formed by an isochronous vapordepositing of at least one element from the Group which contains theelements from the 4th, 5th and 6th Subgroup and silicon, according to aprocess of claim 44 and a plasma-aided depositing of carbon from the gasphase, additionally, a carbon-containing gas, being used as the reactiongas.
 54. Process according claim 53, wherein, as the thickness of thetransition layer increases, the fraction of the carbon depositing isincreased continuously or in steps.
 55. Process according to claim 43wherein, the adamantine carbon layer forming the cover layer isgenerated by the plasma CVD deposition of carbon from the gas phase witha carbon-containing gas being used as the reaction gas.
 56. Processaccording to claim 53, wherein the reaction gas for depositing carbon,in addition to the carbon-containing gas, comprises at least onehydrogen and a noble gas.
 57. Process according to claim 56, wherein,during the depositing of the cover layer made of adamantine carbon, atleast one of the fraction of the carbon-containing gas is increased andthe fraction of the noble gas is lowered.
 58. Process according to claim1, wherein a unipolar or bipolar substrate bias voltage is applied tothe substrate, which is pulsed in a medium frequency range of from 1 to10,000 kHz.
 59. Process according to claim 58, wherein the substratebias voltage is sinusoidal or is pulsed such that long negative andshort positive pulse periods or large negative and low positiveamplitudes are applied.
 60. Process according to claim 43, wherein,during at least one of the cleaning of the surface and the applicationof the adhesive layer and the application of transition layer and theapplication of cover layer made of an adamantine carbon, a longitudinalmagnetic field with a uniform line of flux course is superimposed on thesubstrate, the magnetic field being variable continuously or in stepswith respect to at least one of time and space.
 61. Process according toclaim 43, wherein said at least one of the application of the adhesivelayer and the transition layer and the cover layer of adamantine carbontakes place at a pressure of from 10⁻⁴ mbar to 10⁻² mbar. 62.Arrangement for coating one or several substrates, particularly for theimplementation of the coating process for the protection against wear,for the protection against corrosion and for improving the slidingproperties and the like, having an adhesive layer for the arrangement ona substrate, a transition layer for the arrangement on the adhesivelayer and a cover layer of an adamantine carbon, said arrangementincluding substrate holding devices for receiving the substrates to becoated, at least one gas supply unit for the metered addition of processgas, at least one vaporizer device for providing coating material forthe vapor depositing, an arc generating device for igniting adirect-voltage low-voltage arc, a device for generating a substrate biasvoltage, and having at least one or several magnetic field generatingdevices for forming a magnetic far field.
 63. Arrangement according toclaim 62, wherein the magnetic field generating device is formed by atleast one Helmholtz coil.
 64. Arrangement according to claim 63, whereinthe Helmholtz coil can be controlled with respect to the produciblemagnetic flux density.
 65. Arrangement according to claim 62, whereinthe arrangement for generating a substrate bias voltage is designed suchthat the substrate bias voltage can be varied continuously or in stepswith respect to at least one of a preceding sign and an amount of theapplied substrate bias voltage and can be operated in a bipolar orunipolar manner with a frequency in a medium frequency range. 66.Arrangement according to claim 62, wherein the vaporizer devicecomprises at least one sputter targets, arc sources, thermal vaporizers,crucibles heated by low-voltage arcs and other thermal evaporationapparatus.
 67. Arrangement according to claim 62, wherein the vaporizerdevice is able to separated from the remaining process chamber. 68.Arrangement according to claim 62, wherein the arrangement comprises asubstrate heating system in the form of one of an inductive heater and aradiant heater.
 69. Arrangement according to claim 62, wherein the arcgenerating device comprises an ion source and an anode as well as adirect voltage supply, the ion source being connected with the negativepole of the direct voltage supply.
 70. Arrangement according to claim69, wherein the positive pole of the direct voltage supply is able to beconnected with the anode or the substrate holding devices. 71.Arrangement according to claim 69, wherein the ion source comprises afilament made of one of tungsten and tantalum, which is arranged in anionization chamber which can be separated from the process chamber by ascreen, made of one of tungsten and tantalum.
 72. Arrangement accordingto claim 62, wherein, the substrate holding devices are movable, aboutat least one or several axes.
 73. Arrangement according to claim 62,wherein, in addition, permanent magnets are provided for generating amagnetic near field.
 74. Arrangement according to claim 73, wherein theadditional permanent magnets are constructed in a ring shape around thevacuum chamber with an alternating pole alignment, and are constructedas an magnetron electron trap.
 75. The process according to claim 43,wherein the adhesive layer comprises at least one element from the Groupwhich contains the elements of the 4th, 5th and 6th Subgroup andsilicon, the transition layer comprises carbon and at least one elementfrom the Group which contains the elements of the 4th, 5th and 6thSubgroup as well as silicon, and the cover layer comprises essentiallyadamantine carbon, the layer system having a hardness of at last 15 GPa,and an adhesion of at least 3 HF, on a substrate.
 76. The arrangementaccording to claim 62, wherein the adhesive layer comprises at least oneelement from the Group which contains the elements of the 4th, 5th and6th Subgroup and silicon, the transition layer comprises carbon and atleast one element from the Group which contains the elements of the 4th,5th and 6th Subgroup as well as silicon, and the cover layer comprisesessentially adamantine carbon, the layer system having a hardness of atlast 15 GPa, and an adhesion of at least 3 HF, having a vacuum chamberwith a pumping system for generating a vacuum in the vacuum chamber,